Fabrication of sub-micrometer sized Er:CaF2 transparent ceramics for eye-safe lasers

The 1 at.% Er:CaF2 transparent ceramics were prepared by the air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized by the co-precipitation method. The influence of pre-sintering temperature and HIP post-treatment on the density, microstructures, optical and photoluminescence properties of Er:CaF2 ce-ramics were investigated. After HIP post-treatment (650 degrees C x 2 h, 100 MPa Ar), the pores in the pre-sintering ceramics were gradually eliminated and high transparency was achieved. The maximum in-line transmittance of the HIPed 1 at.% Er:CaF2 reaches 90.5% at 1600 nm (2.8 mm thickness) when the pre-sintered temperature is 625 degrees C.The absorption cross section was calculated. The strong absorption peak at 1530 nm reveals an unfa-vorable infrared emission. The main emission peak at 1530 nm, which is derived from the 4I13/2 -> 4I15/2 transition of Er3+, can be observed under excitation of 980 nm. Owing to the long lifetime of 4I13/2 (32.3 ms) and large emission cross section, the 1 at.% Er:CaF2 transparent ceramics have great potential to achieve a good NIR laser performance in the 1.5 mu m region.